Andrew Nicols
594 lines
25 KiB
PHP
594 lines
25 KiB
PHP
<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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namespace core_cache;
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use core\exception\coding_exception;
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/**
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* A session cache.
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*
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* This class is used for session caches returned by the cache::make methods.
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*
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* It differs from the application loader in a couple of noteable ways:
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* 1. Sessions are always expected to exist.
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* Because of this we don't ever use the static acceleration array.
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* 2. Session data for a loader instance (store + definition) is consolidate into a
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* single array for storage within the store.
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* Along with this we embed a lastaccessed time with the data. This way we can
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* check sessions for a last access time.
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* 3. Session stores are required to support key searching and must
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* implement searchable_cache_interface. This ensures stores used for the cache can be
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* targetted for garbage collection of session data.
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*
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* This cache class should never be interacted with directly. Instead you should always use the cache::make methods.
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* It is technically possible to call those methods through this class however there is no guarantee that you will get an
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* instance of this class back again.
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*
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* @todo we should support locking in the session as well. Should be pretty simple to set up.
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*
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* @internal don't use me directly.
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* @method store|searchable_cache_interface get_store() Returns the cache store which must implement
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* both searchable_cache_interface.
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*
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* @package core_cache
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* @category cache
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* @copyright 2012 Sam Hemelryk
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class session_cache extends cache {
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/**
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* The user the session has been established for.
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* @var int
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*/
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protected static $loadeduserid = null;
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/**
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* The userid this cache is currently using.
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* @var int
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*/
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protected $currentuserid = null;
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/**
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* The session id we are currently using.
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* @var array
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*/
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protected $sessionid = null;
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/**
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* The session data for the above session id.
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* @var array
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*/
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protected $session = null;
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/**
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* Constant used to prefix keys.
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*/
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const KEY_PREFIX = 'sess_';
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/**
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* This is the key used to track last access.
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*/
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const LASTACCESS = '__lastaccess__';
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/**
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* Override the cache::construct method.
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*
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* This function gets overriden so that we can process any invalidation events if need be.
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* If the definition doesn't have any invalidation events then this occurs exactly as it would for the cache class.
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* Otherwise we look at the last invalidation time and then check the invalidation data for events that have occured
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* between then now.
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*
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* You should not call this method from your code, instead you should use the cache::make methods.
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*
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* @param definition $definition
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* @param store $store
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* @param loader_interface|data_source_interface $loader
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*/
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public function __construct(definition $definition, store $store, $loader = null) {
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// First up copy the loadeduserid to the current user id.
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$this->currentuserid = self::$loadeduserid;
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$this->set_session_id();
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parent::__construct($definition, $store, $loader);
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// This will trigger check tracked user. If this gets removed a call to that will need to be added here in its place.
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$this->set(self::LASTACCESS, cache::now());
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$this->handle_invalidation_events();
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}
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/**
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* Sets the session id for the loader.
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*/
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protected function set_session_id() {
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$this->sessionid = preg_replace('#[^a-zA-Z0-9_]#', '_', session_id());
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}
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/**
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* Returns the prefix used for all keys.
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* @return string
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*/
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protected function get_key_prefix() {
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return 'u' . $this->currentuserid . '_' . $this->sessionid;
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}
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/**
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* Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.
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*
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* This function is called for every operation that uses keys. For this reason we use this function to also check
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* that the current user is the same as the user who last used this cache.
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*
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* On top of that if prepends the string 'sess_' to the start of all keys. The _ ensures things are easily identifiable.
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*
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* @param string|int $key As passed to get|set|delete etc.
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* @return string|array String unless the store supports multi-identifiers in which case an array if returned.
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*/
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protected function parse_key($key) {
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$prefix = $this->get_key_prefix();
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if ($key === self::LASTACCESS) {
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return $key . $prefix;
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}
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return $prefix . '_' . parent::parse_key($key);
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}
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/**
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* Check that this cache instance is tracking the current user.
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*/
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protected function check_tracked_user() {
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if (isset($_SESSION['USER']->id) && $_SESSION['USER']->id !== null) {
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// Get the id of the current user.
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$new = $_SESSION['USER']->id;
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} else {
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// No user set up yet.
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$new = 0;
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}
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if ($new !== self::$loadeduserid) {
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// The current user doesn't match the tracked userid for this request.
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if (!is_null(self::$loadeduserid)) {
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// Purge the data we have for the old user.
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// This way we don't bloat the session.
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$this->purge();
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}
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self::$loadeduserid = $new;
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$this->currentuserid = $new;
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} else if ($new !== $this->currentuserid) {
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// The current user matches the loaded user but not the user last used by this cache.
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$this->purge_current_user();
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$this->currentuserid = $new;
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}
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}
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/**
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* Purges the session cache of all data belonging to the current user.
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*/
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public function purge_current_user() {
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$keys = $this->get_store()->find_by_prefix($this->get_key_prefix());
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$this->get_store()->delete_many($keys);
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}
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/**
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* Retrieves the value for the given key from the cache.
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*
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* @param string|int $key The key for the data being requested.
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* It can be any structure although using a scalar string or int is recommended in the interests of performance.
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* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
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* @param int $requiredversion Minimum required version of the data or cache::VERSION_NONE
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* @param int $strictness One of IGNORE_MISSING | MUST_EXIST
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* @param mixed &$actualversion If specified, will be set to the actual version number retrieved
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* @return mixed|false The data from the cache or false if the key did not exist within the cache.
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* @throws coding_exception
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*/
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protected function get_implementation($key, int $requiredversion, int $strictness, &$actualversion = null) {
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// Check the tracked user.
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$this->check_tracked_user();
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// Use parent code.
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return parent::get_implementation($key, $requiredversion, $strictness, $actualversion);
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}
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/**
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* Sends a key => value pair to the cache.
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*
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* <code>
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* // This code will add four entries to the cache, one for each url.
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* $cache->set('main', 'http://moodle.org');
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* $cache->set('docs', 'http://docs.moodle.org');
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* $cache->set('tracker', 'http://tracker.moodle.org');
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* $cache->set('qa', 'http://qa.moodle.net');
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* </code>
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*
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* @param string|int $key The key for the data being requested.
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* It can be any structure although using a scalar string or int is recommended in the interests of performance.
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* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
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* @param mixed $data The data to set against the key.
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* @return bool True on success, false otherwise.
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*/
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public function set($key, $data) {
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$this->check_tracked_user();
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$loader = $this->get_loader();
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if ($loader !== false) {
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// We have a loader available set it there as well.
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// We have to let the loader do its own parsing of data as it may be unique.
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$loader->set($key, $data);
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}
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if (is_object($data) && $data instanceof cacheable_object_interface) {
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$data = new cached_object($data);
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} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($data)) {
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// If data is an object it will be a reference.
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// If data is an array if may contain references.
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// We want to break references so that the cache cannot be modified outside of itself.
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// Call the function to unreference it (in the best way possible).
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$data = $this->unref($data);
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}
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// We dont' support native TTL here as we consolidate data for sessions.
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if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
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$data = new ttl_wrapper($data, $this->get_definition()->get_ttl());
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}
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$success = $this->get_store()->set($this->parse_key($key), $data);
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if ($this->perfdebug) {
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helper::record_cache_set(
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$this->get_store(),
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$this->get_definition(),
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1,
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$this->get_store()->get_last_io_bytes()
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);
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}
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return $success;
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}
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/**
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* Delete the given key from the cache.
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*
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* @param string|int $key The key to delete.
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* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
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* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
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* @return bool True of success, false otherwise.
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*/
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public function delete($key, $recurse = true) {
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$parsedkey = $this->parse_key($key);
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if ($recurse && $this->get_loader() !== false) {
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// Delete from the bottom of the stack first.
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$this->get_loader()->delete($key, $recurse);
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}
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return $this->get_store()->delete($parsedkey);
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}
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/**
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* Retrieves an array of values for an array of keys.
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*
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* Using this function comes with potential performance implications.
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* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
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* the equivalent singular method for each item provided.
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* This should not deter you from using this function as there is a performance benefit in situations where the cache store
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* does support it, but you should be aware of this fact.
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*
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* @param array $keys The keys of the data being requested.
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* Each key can be any structure although using a scalar string or int is recommended in the interests of performance.
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* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
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* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
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* @return array An array of key value pairs for the items that could be retrieved from the cache.
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* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.
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* Otherwise any key that did not exist will have a data value of false within the results.
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* @throws coding_exception
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*/
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public function get_many(array $keys, $strictness = IGNORE_MISSING) {
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$this->check_tracked_user();
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$parsedkeys = [];
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$keymap = [];
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foreach ($keys as $key) {
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$parsedkey = $this->parse_key($key);
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$parsedkeys[$key] = $parsedkey;
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$keymap[$parsedkey] = $key;
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}
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$result = $this->get_store()->get_many($parsedkeys);
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if ($this->perfdebug) {
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$readbytes = $this->get_store()->get_last_io_bytes();
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}
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$return = [];
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$missingkeys = [];
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$hasmissingkeys = false;
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foreach ($result as $parsedkey => $value) {
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$key = $keymap[$parsedkey];
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if ($value instanceof ttl_wrapper) {
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/* @var ttl_wrapper $value */
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if ($value->has_expired()) {
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$this->delete($keymap[$parsedkey]);
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$value = false;
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} else {
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$value = $value->data;
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}
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}
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if ($value instanceof cached_object) {
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/* @var cached_object $value */
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$value = $value->restore_object();
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} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {
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// If data is an object it will be a reference.
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// If data is an array if may contain references.
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// We want to break references so that the cache cannot be modified outside of itself.
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// Call the function to unreference it (in the best way possible).
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$value = $this->unref($value);
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}
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$return[$key] = $value;
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if ($value === false) {
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$hasmissingkeys = true;
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$missingkeys[$parsedkey] = $key;
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}
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}
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if ($hasmissingkeys) {
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// We've got missing keys - we've got to check any loaders or data sources.
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$loader = $this->get_loader();
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$datasource = $this->get_datasource();
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if ($loader !== false) {
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foreach ($loader->get_many($missingkeys) as $key => $value) {
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if ($value !== false) {
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$return[$key] = $value;
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unset($missingkeys[$parsedkeys[$key]]);
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}
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}
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}
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$hasmissingkeys = count($missingkeys) > 0;
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if ($datasource !== false && $hasmissingkeys) {
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// We're still missing keys but we've got a datasource.
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foreach ($datasource->load_many_for_cache($missingkeys) as $key => $value) {
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if ($value !== false) {
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$return[$key] = $value;
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unset($missingkeys[$parsedkeys[$key]]);
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}
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}
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$hasmissingkeys = count($missingkeys) > 0;
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}
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}
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if ($hasmissingkeys && $strictness === MUST_EXIST) {
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throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');
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}
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if ($this->perfdebug) {
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$hits = 0;
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$misses = 0;
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foreach ($return as $value) {
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if ($value === false) {
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$misses++;
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} else {
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$hits++;
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}
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}
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helper::record_cache_hit($this->get_store(), $this->get_definition(), $hits, $readbytes);
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helper::record_cache_miss($this->get_store(), $this->get_definition(), $misses);
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}
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return $return;
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}
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/**
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* Delete all of the given keys from the cache.
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*
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* @param array $keys The key to delete.
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* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
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* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
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* @return int The number of items successfully deleted.
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*/
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public function delete_many(array $keys, $recurse = true) {
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$parsedkeys = array_map([$this, 'parse_key'], $keys);
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if ($recurse && $this->get_loader() !== false) {
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// Delete from the bottom of the stack first.
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$this->get_loader()->delete_many($keys, $recurse);
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}
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return $this->get_store()->delete_many($parsedkeys);
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}
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/**
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* Sends several key => value pairs to the cache.
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*
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* Using this function comes with potential performance implications.
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* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
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* the equivalent singular method for each item provided.
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* This should not deter you from using this function as there is a performance benefit in situations where the cache store
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* does support it, but you should be aware of this fact.
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*
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* <code>
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* // This code will add four entries to the cache, one for each url.
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* $cache->set_many(array(
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* 'main' => 'http://moodle.org',
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* 'docs' => 'http://docs.moodle.org',
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* 'tracker' => 'http://tracker.moodle.org',
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* 'qa' => ''http://qa.moodle.net'
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* ));
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* </code>
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*
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* @param array $keyvaluearray An array of key => value pairs to send to the cache.
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* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.
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* ... if they care that is.
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*/
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public function set_many(array $keyvaluearray) {
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$this->check_tracked_user();
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$loader = $this->get_loader();
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if ($loader !== false) {
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// We have a loader available set it there as well.
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// We have to let the loader do its own parsing of data as it may be unique.
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$loader->set_many($keyvaluearray);
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}
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$data = [];
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$definitionid = $this->get_definition()->get_ttl();
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$simulatettl = $this->has_a_ttl() && !$this->store_supports_native_ttl();
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foreach ($keyvaluearray as $key => $value) {
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if (is_object($value) && $value instanceof cacheable_object_interface) {
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$value = new cached_object($value);
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} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {
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// If data is an object it will be a reference.
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// If data is an array if may contain references.
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// We want to break references so that the cache cannot be modified outside of itself.
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// Call the function to unreference it (in the best way possible).
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$value = $this->unref($value);
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}
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if ($simulatettl) {
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$value = new ttl_wrapper($value, $definitionid);
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}
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$data[$key] = [
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'key' => $this->parse_key($key),
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'value' => $value,
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];
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}
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$successfullyset = $this->get_store()->set_many($data);
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if ($this->perfdebug && $successfullyset) {
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helper::record_cache_set(
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$this->get_store(),
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$this->get_definition(),
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$successfullyset,
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$this->get_store()->get_last_io_bytes()
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);
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}
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return $successfullyset;
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}
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/**
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* Purges the cache store, and loader if there is one.
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*
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* @return bool True on success, false otherwise
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*/
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public function purge() {
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$this->get_store()->purge();
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if ($this->get_loader()) {
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$this->get_loader()->purge();
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}
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return true;
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}
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/**
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* Test is a cache has a key.
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*
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* The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the
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* test and any subsequent action (get, set, delete etc).
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* Instead it is recommended to write your code in such a way they it performs the following steps:
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* <ol>
|
|
* <li>Attempt to retrieve the information.</li>
|
|
* <li>Generate the information.</li>
|
|
* <li>Attempt to set the information</li>
|
|
* </ol>
|
|
*
|
|
* Its also worth mentioning that not all stores support key tests.
|
|
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
|
|
* Just one more reason you should not use these methods unless you have a very good reason to do so.
|
|
*
|
|
* @param string|int $key
|
|
* @param bool $tryloadifpossible If set to true, the cache doesn't contain the key, and there is another cache loader or
|
|
* data source then the code will try load the key value from the next item in the chain.
|
|
* @return bool True if the cache has the requested key, false otherwise.
|
|
*/
|
|
public function has($key, $tryloadifpossible = false) {
|
|
$this->check_tracked_user();
|
|
$parsedkey = $this->parse_key($key);
|
|
$store = $this->get_store();
|
|
if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
|
|
// The data has a TTL and the store doesn't support it natively.
|
|
// We must fetch the data and expect a ttl wrapper.
|
|
$data = $store->get($parsedkey);
|
|
$has = ($data instanceof ttl_wrapper && !$data->has_expired());
|
|
} else if (!$this->store_supports_key_awareness()) {
|
|
// The store doesn't support key awareness, get the data and check it manually... puke.
|
|
// Either no TTL is set of the store supports its handling natively.
|
|
$data = $store->get($parsedkey);
|
|
$has = ($data !== false);
|
|
} else {
|
|
// The store supports key awareness, this is easy!
|
|
// Either no TTL is set of the store supports its handling natively.
|
|
/* @var store|key_aware_cache_interface $store */
|
|
$has = $store->has($parsedkey);
|
|
}
|
|
if (!$has && $tryloadifpossible) {
|
|
$result = null;
|
|
if ($this->get_loader() !== false) {
|
|
$result = $this->get_loader()->get($parsedkey);
|
|
} else if ($this->get_datasource() !== null) {
|
|
$result = $this->get_datasource()->load_for_cache($key);
|
|
}
|
|
$has = ($result !== null);
|
|
if ($has) {
|
|
$this->set($key, $result);
|
|
}
|
|
}
|
|
return $has;
|
|
}
|
|
|
|
/**
|
|
* Test is a cache has all of the given keys.
|
|
*
|
|
* It is strongly recommended to avoid the use of this function if not absolutely required.
|
|
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
|
|
*
|
|
* Its also worth mentioning that not all stores support key tests.
|
|
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
|
|
* Just one more reason you should not use these methods unless you have a very good reason to do so.
|
|
*
|
|
* @param array $keys
|
|
* @return bool True if the cache has all of the given keys, false otherwise.
|
|
*/
|
|
public function has_all(array $keys) {
|
|
$this->check_tracked_user();
|
|
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
|
|
foreach ($keys as $key) {
|
|
if (!$this->has($key)) {
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
// The cache must be key aware and if support native ttl if it a ttl is set.
|
|
/* @var store|key_aware_cache_interface $store */
|
|
$store = $this->get_store();
|
|
return $store->has_all(array_map([$this, 'parse_key'], $keys));
|
|
}
|
|
|
|
/**
|
|
* Test if a cache has at least one of the given keys.
|
|
*
|
|
* It is strongly recommended to avoid the use of this function if not absolutely required.
|
|
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
|
|
*
|
|
* Its also worth mentioning that not all stores support key tests.
|
|
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
|
|
* Just one more reason you should not use these methods unless you have a very good reason to do so.
|
|
*
|
|
* @param array $keys
|
|
* @return bool True if the cache has at least one of the given keys
|
|
*/
|
|
public function has_any(array $keys) {
|
|
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
|
|
foreach ($keys as $key) {
|
|
if ($this->has($key)) {
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
/* @var store|key_aware_cache_interface $store */
|
|
$store = $this->get_store();
|
|
return $store->has_any(array_map([$this, 'parse_key'], $keys));
|
|
}
|
|
|
|
/**
|
|
* The session loader never uses static acceleration.
|
|
* Instead it stores things in the static $session variable. Shared between all session loaders.
|
|
*
|
|
* @return bool
|
|
*/
|
|
protected function use_static_acceleration() {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Alias this class to the old name.
|
|
// This file will be autoloaded by the legacyclasses autoload system.
|
|
// In future all uses of this class will be corrected and the legacy references will be removed.
|
|
class_alias(session_cache::class, \cache_session::class);
|